New to this site. I got the HP bug and just received a 41CV. I also bought a Time Module for obvious reasons.

When I plug it in (any slot) all I get on the screen is all @ symbols (12 of them) e.g. "@@@@@@@@@@@@". If I look closely, the display seems to blink or pulse at about a 1 second cadence. Off for a very short time and then on so that it looks like it's mostly on. I'm turning off the 41CV first before inserting the module as I'm supposed to. Pressing ON when the @ symbols are displayed does nothing or makes the screen blank. Pressing backspace and ON at the same time does nothing. A few times while writing this and having the 41CV on with the @'s, I heard a single beep of about 1/4 second. I have to remove the batteries to clear the screen and when I power back on after removing the module, I get MEMORY LOST and then I press ON to clear it and ON again and it powers up fine. Sometimes when having the Time Module unplugged for a while, I'll see "@@@@@@ @@@@ " (a space at position 7 and 12 from the left) when I plug in the Time Module and then after a second it goes to all 12 @'s.

Does anyone have any input? Do you think the Time Module is bad? The seller is willing to take it back. The batteries seem to be fairly new and measure 1.47V which is a little low but they work. I have some new batteries on order just in case. There is some very, very slight corrosion on one of the springs of the battery holder and after cleaning it, the unit has powered on consistently. Could power be an issue?

I can't tell you much about HP-41 repairs, but if the problem only shows up with the Time module plugged in, I think there's your culprit. I think you'll find it does the same thing in any of the ports, and I expect you'd find that the calc works fine with any good module (whether Time, memory, application, interface, etc.).

As for the corrosion on the battery contacts, if it's from alkaline batteries, you can clean it up very easily with a Q-tip dampened with vinegar (but not so much that it drips or runs). If it's from acidic batteries, use a baking soda solution instead of vinegar. Someone might add to this. I'm not much of a chemist, but I tried the vinegar on another battery holder (not in a calc) and was very pleasantly surprised how easily and quickly it cleaned it up. Then I used more Q-tips dampened with just water to get the vinegar off and do the final clean-up.

Thanks for the info Garth. After cleaning the spring up a bit, the power ons and offs in general (not related to the Time Module issue) have been consistently working. I'll try some vinegar and see if I can get them super clean.

I've got some new batteries on order. After I put them in, if there is still a problem, then I think you're right - it's the module.

Also, after I posted, I did notice a faint high pitch noice from the module and a "blip" in the noise every second to coincide with the screen flashes. I doubt it's a 32khz noise from the crystal since that's not audible to humans, but it is blipping once a second. Does anyone know if the clock in the Time Module or on the CX keeps track of time in the sub-second range or is 1 second the smallest increment? Just curious since this blipping is at a 1 second frequency as if it's tied to a clock somehow.